Conducting polymers, or polymers that have conjugation in their backbone, can be used in many commercial applications including for example OLEDs, PLEDs, photovoltaic cells, transistors, sensors, and the like. See, for example, The Encyclopedia of Polymer Science and Engineering, Wiley, 1990, pages 298-300, including polyacetylene, poly(p-phenylene), poly(p-phenylene sulfide), polypyrrole, and polythiophene; see also U.S. Pat. Nos. 6,602,974 to McCullough et al. and 6,166,172 to McCullough et al., as well as “The Chemistry of Conducting Polythiophenes,” by Richard D. McCullough, Adv. Mater. 1998, 10, No. 2, pages 93-116 and Handbook of Conducting Polymers, 2nd Ed. 1998, Chapter 9, by McCullough et al., “Regioregular, Head-to-Tail Coupled Poly(3-alkylthiophene) and its Derivatives,” pages 225-258. In many cases, commercial applications compel that these polymers be free of metallic impurities. For example, nickel and magnesium impurities represent typical problems. This can be a challenge however because large amounts of metals can be used in preparing these polymers including magnesium and nickel which may stubbornly persist in the material despite careful workup. Conducting polymers can aggregate and trap impurities, and solubility can be difficult. However, extensive purification can be economically unattractive. Metallic impurities can alter and reduce properties and generally generate confusion in data interpretation. In many cases, one should note the purification methods used for preparing the polymer in reporting the properties of the polymer or devices using the polymer. See for example US Patent Publication 2004/0250849 to Chen et al.; Erwin et al, “Effects of Impurities on the Optical Properties of Poly-3-hexylthiophene Thin Films,” Thin Solid Films, 409 (2002) 198-205. Problems of metallic impurities are particularly relevant to development of polythiophenes and regioregular polythiophenes.
A general need exists to find a versatile, inexpensive, convenient, commercially attractive method to purify polymers, particularly for electronic applications and those involving electric current flow, fields, and interaction with light. The polymers should be electronics grade: high quality and high purity enabling high mobility performance. Relevant applications include organic electronic applications including RFID chips, solar cells, FETs, OLEDs, and PLEDs. Commercial scale should be possible with multi-kg batches. For example, a need exists to prepare polymers for both bench work and at commercial scale wherein the total metal content is less than 50 ppm, the contents of magnesium and nickel are each undetectable, and the amount of iron is also reduced to below 50 ppm.
U.S. Pat. No. 6,894,145 provides one approach based on extraction.